Let's decompose the error message...

<STDIN> line 1

One line has been read from STDIN. (which is true at line 38)

at Webcrawler.pl line 38

The problem is in the file 'Webcrawler.pl' on line 38.

Undefined Subroutine &main::get called

You attempted to call the function 'get' in the 'main' (default) namespace, but the function wasn't defined.

So ... looking at line 38:

You're attempting to assign to the scalar $webcrawler the returned value from get($url_name)

More than likely, what you wanted to do was to call the 'get' method on $webcrawler, which is a WWW::Mechanize object:

Of course, from looking at the documentation from WWW::Mechanize, you'd see that get returns an HTTP::Response object, which you'll most likely want to assign to something, so you can interact with it.